Tom Lawrence’s free-kick was enough for victory at Preston as fifth-placed Derby ended an eight-game winless run.
Alan Browne’s first-half penalty failure proved costly for North End, who missed the chance to leapfrog Derby into the Championship play-off places.
Browne hit the post from the spot after he had been fouled by Andre Wisdom.
A Derby side showing five changes from Friday’s abject 4-1 home defeat by Sunderland did not have a shot at goal until Lawrence’s 52nd-minute winner.
The Rams had slipped from second in the division in the two months since their previous victory, and faced the prospect of dropping out of the top six had they not gained a positive result at Deepdale.
Preston enjoyed the better of the first half but Callum Robinson was the only player to test Scott Carson, the Derby goalkeeper saving his angled shot, while the former Aston Villa forward also headed and shot off target with further chances.
After Lawrence’s goal, North End duo Paul Huntington and Paul Gallagher fired over with snapshots in the box but they were unable to find an equaliser.
Derby managed only two attempts at goal in the whole match, but should have extended their lead through substitute Kasey Palmer, who fired wide from 12 yards.